We've now published the source code for 2 of our 3 authoring AddIns on GitHub:
https://github.com/plutext/OpenDoPE-Mapping-WordAddIn is the most commonly used addin, similar to Word 2013's XML Mapping Pane, but with support for OpenDoPE content controls, including binding:
* pictures (including as rich text, for more positioning flexibility)
* Flat OPC XML
https://github.com/plutext/OpenDoPE-NoXML-WordAddIn uses a simple fixed format for the XML, so the author doesn't need to see it; it is currently targeted at the interactive use case, but the various forms could be simplified to cover non-interactive easily enough. If you want to try this one out (there's a bit of polishing required before it is ready for final release), there's an installer at https://github.com/plutext/OpenDoPE-NoX ... e?raw=true
Unlike docx4j (which is ASL v2 licensed), the source code for these addins is published under the GPL. This is to encourage contribution of fixes/improvements.
(Our oldest addin we haven't published, mainly because we suspect dev effort is better focused on the 2 we have published)
Enjoy .. Jason